Alternating-current machine.



, No. 811,304. PATENTED JAN? 30,1905. M. 0. A; LATOUR.

ALTERNATING CURRENT; MACHINE.

\PPLIOATION FILED JUNE 25, 1904.

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.at Paris,

MARIUS CHARLES.ARTHUR LATOUR, OF FARIS, FRANCE, ASSIGNOR TO GENERALELECTRIC COMPANY,

A CORPORATION OF NEW YORK.

ALTERNATlNG-OURRENT MACHINE.

Specification of Letters Patent.

Patented Jan. 30, 1906.

Application filed June 25, 1904:. Serial No. 214,093i

To all whom it Worry concern:

Be it known that I, MARIUS CHARLES AR- THUR LATOUR, a citizen of France,residing France, have invented certain new and useful Improvements inAlternating- Current Machines, of which the following is aspecification.

My invention relates to alternating-current machines of the commutatortype; and its object is to provide novel commutating means for suchmachines, whereby sparking at the commutator is eliminated.

Commutation in alternating-current machines presents difiiculties whichare absent in direct-current machines fsince m an alternating-currentmachine the coil which is shortcircuited at the instant ofcommutation issubject to an alternating or pulsating field. Various methods ofreducing sparking have been devised; but bymy invention I remove thecause of the sparking, since I so arrange the commutator-brushes that nocoils are shortcircuited within the machine during commutation, and,furthermore, I. do not accomplish this end by open-circuiting thearmature, as has been done in some of the arrangements proposedheretofore:

It is a well-known characteristic of the series or wave winding thatonly a single pair of brushes are re uired for a multipolar machine,since all oi the armature-winding is in series. I take advantage of thisfact by providing acommutator havingalternate live and dead segments andemploying a plurality of brushes of each around the commutator of awidth no greater than that of a commutator-segment. only a single pairof brushes were used, the armature-circuit would be opened every time adead segment passed a brush; but by employing a second set of brushesconnected in parallel with the first and so arranging the second setthat they are in engagement with live segments at the instant that thefirst set are in engagement with dead segments I maintain thearmature-circuit always closed, although the circuit of each brush iscontinually opened and closed.

With the arrangement as outlined above it is evident that no shortcircuit can be produced by a single brush, since no single brush is wideenough to engage two live segments at the same time. Consequently noshort polarity distributedcircuits can exist within the machine. Theonly short circuits that can exist are between the parallel-connectedbrushes of the same polarity, and since this connection is outside ofthe machine not only may a resistance be inserted in the connection tolimit the flow of current, but also the amount of resistance may readilybe controlled. The latter point is especially important in the case ofalternating-current motors, since at starting the induced electromotiveforce in the short-circuited armature-coils is large, while atsynchronism it is small. Consequently if sufiicient resistance beinserted in the commutator-leads, as has been proposed heretofore, tolimit properly the short-circuited current at starting a great deal ofpower would be wasted when the motor is operating near synchronism. Bymeans of my invention the motor may be started with sufficientresistance between the parallel-connected brushes to limit theshort-circuited current to any desired amount, and this resistance maybe cut out as the motor comes up to speed.

My invention also comprises as a further feature the combination, withan alternatingcurrent machine, ofitwo commutators oi the type describedabove connected to opposite ends of the armature-conductors, a pluralityof brushes bearing on each commutator, and resistances connectingbrushes of the same polarity. The use of the additional commutatordecreases current fluctuation in the armature and improves theefiiciency and operation of the motor. In this aspect my invention isnot limited to a multipolar machine or to a wave-wound armature, sinceby the use of two commutators a plurality of brushes of each polaritymay be employed, even in a bipolar machine.

My invention will best be understood from the accompanying drawings, inwhich Figure 1 shows diagrammatically a fourpole series or wave windingprovided with a commutator and-brushes in accordance with my invention.Fig. 2 shows a six-pole series winding similarly provided. Fig. 3 showsdiagrammatically an arrangement for cutting out the resistance betweenparallel-ebnnected brushes, and Fig. 4 shows a diflej'ent connection ofthe resistances adapted for a repulsion-motor.

In Fig. 1, A represents the armature-wind r three of the brushes B Blarity and the other brushes being of the oplarly ing, which is shown asthe well-known series I of resistance in the short-circui-ting connecorwave winding developed on a plane surface. The commutator C is providedwith alternate conducting-segments connected to the winding and dead sements disposed between the conducting or Iive segments. The deadsegments may be made of insulating material, as shown, or may becomposed of conducting material simply insulated from the live segments.Four brushes are shown bearing on the commutator C, the brushes of thesame polarity being indicated by the same letters. Thus B B representbrushes of one polarity, and B B brushes of the opposite polarity. Ifthe brushes are symmetrically distributed around the commutator, asshown, the commutator is arranged with an odd number ofconducting-segments, so that when one brush is on a live segmentthe'other brush of the same polarity is on a dead segment. The brushesof the same polarity are connected through a resistance designed tolimit properly the amount of short-circuited current. Thus the brushes BB are connected by a resistance R, a tap T fromthe center of theresistance forming one terminal of the armature. The brushes of oppositeolarity B B are similarly connected throug resistanoe R. Although onecbmmutator, as described, is suflicient for the purpose of my invention,I have shown in Fig. 1 a second com- 'inutator C for a reason that willbeexplained ater.

In Fig. I have shown my invention simiapplied to the six-pole winding.With s arrangement six sets of brushes are used,

B being of one poposite polarity. The brushes B B B are con nected throuh the resistances R R R, and brushes -B' B are similarly connectedthrough theresistances R R R. The 0 eration with bothof-these windingsis t e same as has been heretofore described. The current is shiftedfrom one brush to another brush of the sameJpolarity and back again asa-dead segment passes first one brush and then the other. N 0 shortcircuits exist within the machine, and the circuit of thearmature-Winding is never opened,- although the circuits of the severalbrushes are continually opened in succession.

In order'to reduce any fiuctuationswhich may result" from shifting; thecurrent from one brush to another, two commutators may be employed, asshown in the figures, and a l the positive gether, as shown in Fig.2, inwhich the positive brushes bearing on one commutator are connected tothose bearing on the other commutator through the resistances R Theseresistances merely supplement the resistances R and R and may be omittedentirely.

As has been said heretofore, since the resistance is external to themachine the amount nate live and dead segments,

- sistance.

brushes may be connected to-' tion may be varied, as desired, to meetvarying conditions of operation. Thus in Fig. 3 the resistance R,connecting'brushes B B, is shown arranged to be varied, the terminals Talways being connected to the central point on the resistance. Theterminals T T represent the terminals of the armature-winding, and thearrangement shown is adapted for improving the commutation of anyvariablespeed machine of the commutator typeas, for instance, analternating-current series motor. In the special case of arepulsionmotor the terminals T T would be connected, the operation beingthe same as already described. Another method of connecting the brushesthrough resistances is shown in Fig. 4. This connection, which is suitedfor a repulsion-motor, places all the brushes in a closed circuit, withvariable resistances for limiting the amount of current-flowin thearmature-circuits. As resistances are cut out the four brushes areshort-circuited directly on each other.

What I claim-as new, and desire to secure by LettersPatent of the UnitedStates, is

1. In an alternating-current machine, a multipolar field-magnet, awave-armature winding, a commutator composed of alternate live and deadsegments, and a plurality of brushes of each polarity'distributed aroundsaid commutator, the width of a brush being not greater than that of asegment.

2. In an alternating-current machine, a multipolar field-magnet, aWave-,armature winding, a commutator composed of altera plurality ofbrushes of each polarity distributed around said commutator, the widthof a-brush being not greater than that of a segment, and resistancesconnecting brushes of like polarity. 3. In an alternating-currentmachine, a multipolar field-magnet, a wavearmature winding, a commutatorcomposed of alternate live and dead segments, a plurality of brushes ofeach polarity distributed around said commutator, the width of a brushbeing not greater than that of a segment, resistances connecting brushesof like polarity, and means .for varying the amount of sald re- 4. In analternating-current motor, a multipolar field-magnet, a wave-armaturewinding, a commutator composed of alternate live and dead segments, aplurality of brushes of each polarity distributed aroundsaid commutator,the width of a brush being not greater than that ofa segment,resistances connecting brushes of like olarity, and means for cuttingout said reslstances when the motor comes up to speed.

5. In an alternating-current machine, a multipolar field-magnet, awave-armature winding, a) commutator therefor having alternate live anddead segments, a plurality of brushes of each polarity distributedaround said commutator, said brushes being so arranged that one brush ison a live segment when another brush of the same polarity is on a deadsegment.

6. In an alternating-current machine, a multipolar fieldmagnet, aWave-armature winding, a commutator therefor having alternate live anddead segments, a plurality of brushes of each polarity distributedaround said commutator, the width of a brush being not greater than thatof a segment and said brushes being so arranged that one brush is on alive segment when another brush of the same polarity is on a deadsegment, and resistances connecting brushes of the same polarity.

7. In an alternating-current machine, two commutators connected toopposite ends of the armature-conductors, each commutator havingalternate live and dead segments, brushes bearing on said commutator-s,and

on live segments, and resistances interconnecting the brushes of thesame polarity.

In witness whereof I have hereunto set my hand this 24th day of June,1904.

MARIUS CHARLES ARTHUR LATOUR.

Witnesses:

EDWARD WILLIAMS, J r., L. A. HAWKINS.

ment other brushes of the same polarity are

